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battery light on, and other electrical problems

PostPosted: 25 Jan 2006, 10:07
by jifop
Hey ho dudio's,

got a weird one going on, when running the battery light on the vette is always on but very dim, you can only see it at night also in the mornings the battery is run down (it takes ages to start but when i use a booster it fires first time)

it did this with the old alternator so i replaced it and it still does it, and it has a new battery

any ideas?

PostPosted: 25 Jan 2006, 10:56
by Neilyman
Sounds like a dodgy alternator. Try this, when you park it up at night, unplug the alternator. Plug it back in in the morning, if the battery`s ok & the car starts, the alternators duff, probably the diode pack!

PostPosted: 25 Jan 2006, 12:26
by grim_b
Have you fitted any ICE (Stereo) equipment lately? I once had a head unit that needed a perminant power feed to be used without the ignition being on. End result was the head unit's memory and the remote for the amp was draining the battery each night (because it never turned off), but it would really depend on how far you drive each day and how new that battery is before you saw the problem again.

Just a thought tho :lol:

PostPosted: 25 Jan 2006, 21:55
by jifop
defo not the alternator, i put the 6 month old one from the blue chevette on when i first noticed this problem, when that didnt cure it i bought a new alternator. i'd say that eliminates it from the equation.

i did have a sterio in the car but i took it out hoping it might cure this problem but no :(

i guess the next step is to use an ammeter on the car when the ignition is off and try to sus where its going, i guess it must be a shaort somewhere?

PostPosted: 25 Jan 2006, 22:50
by Shuvit-pinto

Try changing your earth lead from the engine to the chassis. If it gets internaly corroded or full of grease and muck it can affect the charge and start process.

I had this on my Pinto Chevette, changed the earth lead and no more probs.

PostPosted: 27 Jan 2006, 00:22
by Doive
My car does this too, although it takes a few days without use to properly flatten the battery. Starting is very lazy, and sometimes when driving at night the battery light glows faintly. I do have a stereo fitted which draws a permanent live feed, but this had been fitted for ages before this started to happen. I'm not too bothered about it.

PostPosted: 29 Jan 2006, 22:17
by shuvit-tim
i'd have said bad earth or badly wired alternator?

PostPosted: 29 Jan 2006, 23:28
by Doive
I gave my charging system a good once over before christmas, and the voltmeter across the battery was showing 12.6V engine off, and 14.0V engine idling when warm. I reckon these are fairly good values, although I'd tend to agree with Tim's diagnosis - my earthing cables are looking slightly suspect. New ones are cheap enough, and easily made to the correct length. I'll have to get some for the sake of changing them.

I don't actually think my problem is as bad as I made out, come to think of it. The battery goes flat over a couple of weeks, not days. Not quite sure why I said that. Old memory obviously failing :lol:

PostPosted: 30 Jan 2006, 00:13
by Harry Flatters
IIRC (Neil, can you confirm?!), the ignition light is operated by a voltage difference between the alternator and the battery (actually, between the alternator and ignition circuit); so if the light's glowing dimly, it implies that there's a small voltage difference where there shouldn't be. Favourite's alternator failure' but could also be a dodgy connection in the +ve circuit as well as earth, assuming you're not trying to load the alternator more than it can cope with.

Assuming the battery tests OK - i.e. fully charged, in good order, no duff cells - take the leads off the alternator and switch the ignition on. Check the voltage between each lead and a good earth. The reading should be pretty much battery voltage - if it's lower, there's a dodgy connection.

Reconnect everything, run the engine at around 3000 rpm and switch all the loads you can on - lights, blower, hrw, etc. Check the voltage across the battery positive and alternator positive terminals, and then the battery negative and alternator negative terminals (or normally, the alternator body). If the meter shows more than 0.5V on the +ve or 0.25V on the -ve you've got connection problems.